In a manufacturing process of a brass-plated steel wire represented by a steel cord of a reinforcing material for tires, a pre-drawing is performed generally by dry drawing, and then, a perlite steel structure is built by a patenting thermal treatment, followed by brass plating on the surface of a steel wire rod, and the steel wire rod is subjected to a wet drawing which is a final wire drawing process. As a means for brass plating, a thermal diffusion plating method in which zinc plating is performed on a copper plated layer, and then a brass-plated layer is created by thermal diffusion, is generally employed.
Examples of a technique relating to improvement of a method for manufacturing a brass-plated steel wire include Patent Document 1. Patent Document 1 relates to a method for manufacturing a brass plated bead wire in which a steel wire is plated with copper and zinc sequentially, and then a thermal treatment which corrects wire drawing strain and a thermal diffusion of copper and zinc plated on the steel wire are simultaneously allowed to proceed, and thereafter, the steel wire is subjected to a pickling treatment by an inorganic acid. A brass plated bead wire in which the adhesive properties with rubber are improved without compromising the mechanical properties can thus be obtained.